Multiple accounts per household are allowed, but only one person per household can take part in a particular study. We have a mechanism in place that stops participants with the same IP address accessing a study.
Please keep in mind that a household is anyone sharing an IP address with you. This is at home, your workplace, school, etc.
Here is an example:
Person A and B are from the same household.
Person A participates in Study X
Person B will then automatically be ineligible for Study X, and will only be able to take part in studies that person A has not completed, and vice versa.